Anyone recommending that you wait until TTK's release is likely giving you the best advice. That said since you just started now, if you have not yet preordered The Taken King yet you might as well do it now. Not because I recommend it as a good value (Because I actually think its a little overpriced and I'm skeptical I would even like it at this point) but because if you are not planning on buying the DLC you might as well stop playing because you will be locked out of a ton of important stuff like weekly and nightfall activities and the Iron banner event once it releases, severely affecting the game you just started. As others have said in the forums the new DLC will "rebalance" a lot of weapons and supposedly bring new "Better" guns than the current ones so focus on keeping exotics, those will still be useful beyond TTK. (P.S. I now feel dirty after having recommended TTK to someone on the forum but your circumstances are special since you are a new player).